1. Field of the Invention
This invention relates to a finely divided silica treated with amidosiloxanes for use in silicone elastomers.
2. Description of the Prior Art
In the silicone elastomer art, the treatment of reinforcing silica fillers is now well known as a means of preventing or retarding the reaction between the surface of the silica filler and the silicone polymer which produces "structuring" or "crepe aging." Structuring results in a subsequent loss of workability of the mixture. U.S. Pat. No. 3,243,404 by Martellock describes silicone compositions containing silylamine or silazane materials as process aids for use in preventing such undesirable reactions. U.S. Pat. No. 3,635,743 by H. Smith describes the use of a process of contacting the filler first with ammonia and then with hexamethyldisilazane. U.S. Pat. No. 4,116,919 by Janet L. Elias, Chi-Long Lee, and Myron T. Maxson, assigned to the same assignee as the present application, discloses the use of reinforcing silica treated with bis-Si(1-methyl-1-silacyclopentenyl)amine and silazane in silicone elastomer compositions.
It has been found that the material used to treat reinforcing silica may have a significant effect upon the properties of the silicone elastomer base produced therefrom and upon the properties of a resulting cured silicone elastomer. The nature of the polydiorganosiloxane fluid used, as well as, the curing mechanism selected both interact with the treated filler to determine the properties of the silicone elastomer base and the cured silicone elastomer. New types of cure systems, as well as, new methods of molding have created a need for novel treatments of reinforcing silica used in the manufacture of silicone elastomers. U.S. Pat. No. 4,008,198 by Krohberger, et al., discloses compositions which are convertible to highly transparent or optically clear elastomers, for example, comprising an organopolysiloxane, a nitrogen containing compound, a hexaorganodisilazane, and silicon dioxide filler.